I have a wall and ceiling crack that must follow where 2 sections of the building ( ablock of flats) were joined together. I filled it well about 18 months ago but it has opened up again. What can I best fill it with to allow for the movement? Thanks

Hello Rosebery, the crack goes vertically up a wall of a corridor, across the ceiling of the corridor at a right angle and down the opposite wall. It's not very wide 1 mm maybe and I don't think there is any depth to it to speak of. It really is as if 2 sections of the building must have been joined together at that point. Thanks for the interest. What do you suggest?